The reversibility of disuse osteoporosis. Fluoride treatment and bone strength.

The biomechanical strength of femur of adult rats was tested after immobilization for 9 weeks and remobilization for 12 weeks of 1 hind leg. Some rats were also given a fluoride supplement of 200 ppm in the drinking water. As reflected in the ultimate torque and stiffness there was a decrease in bone strength due to immobilization. After 12 weeks of remobilization the stiffness remained lower than in normal animals of the same age. Fluoride supplement partially counteracted the effect of immobilization but after the remobilization period no positive effect of the fluoride supplement was observed. Remobilization per se is of much more significance than fluoride in restoration of bone strength.